GstWebRTC - Custom Signaling

GstWebRTC
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Signaling 1.Predefined Signaling 2.Custom Signaling 3.API Reference 4.Advance Settings Plugin Elements 1.GstWebRTCBin 2.GstWebRTCBin Properties 3.GstWebRTCBin Features 1.Data Channel
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This page provides the basics on how to implement custom signalers. In particular, this page describes how to integrate the custom signaler with the project's build system. The API Reference shows how to develop a custom signaler that interacts with GstRrWebRTC state machine.

Custom Signaling Basics

Custom signalers are implemented by subclassing the GstBaseSignaler class. By doing so, the new signaler is integrated into GstRrWebRTC state machine logic. The diagram in Figure 1 summarizes the concept:

Figure 1. UML Diagram of Concrete Signalers

Integrating a Custom Signaling

There are two ways a custom signaler can be integrated into the project. The first one is to build the new signaler along with the GstRrWebRTC project. In this case the signaler will be part of the project's binaries and the signaler's properties will be shown in the inspect output. The second way to integrate an external signaler is by doing it at runtime via the signaler-obj. In this case the signaler is built in an independent project and passed to the WebRTC state machine at runtime. The following subsections present further details.

Integrating Into GstRrWebRTC Project

The easiest way to integrate a custom signaler is to extend the project's build system to construct the new code. The following points summarize the steps necessary to integrate a custom signaler named GstExampleSignaler.

1. Specify the new sources:

At the end of gst/webrtc/Makefile.am:

libgstrrwebrtc_la_SOURCES += gstexamplesignaler.c
noinst_HEADERS += gstexamplesignaler.h

2. Specify extra compile and link flags (if needed):

At the end of gst/webrtc/Makefile.am:

libgstrrwebrtc_la_CFLAGS += -I/usr/include/dependency
libgstrrwebrtc_la_LIBADD += -L/usr/lib/dependency -ldependency

Alternatively, for advanced users, if the dependencies export a pkg-config file, the PKG_CHECK_MODULES may be used in the configure.ac and use the generated flags in this makefile.

3. Regenerate Makefiles:

At the root of the project:

./autogen.sh
make
sudo make install

Integrating From ExternalProject

An alternative way to integrate an external signaler is to do it at runtime via the signaler-obj property. This is specially useful for signalers whose licensing is different and more restrictive than the one shipped with GstRrWebRTC. As such, the signaler can be distributed independently.

If both the signaler-obj and the built-in signaler properties are set, the last property set will be the one finally configured.

Programmatically, an application would set the new signaler in the GstRrWebRTC element similar to the following:

GstElement * webrtcbin;
GstExampleSignaler *examplesignaler;

...

g_object_set (webrtcbin, "signaler-obj", GST_BASE_SIGNALER(example signaler), NULL);